This section provides background information related to the present disclosure which is not necessarily prior art. Oxygen sensors are commonly used in automotive vehicle applications to improve fuel economy, ensure smooth performance, and reduce exhaust emissions. More specifically, oxygen sensors are typically located in the exhaust system before and after the exhaust catalyst in order to determine catalyst efficiency. In this way, pre-catalyst and post-catalyst signals may be monitored and adjusted to meet emissions regulations. Most vehicles today include from 2 to 4 oxygen sensors, but additional sensor use is anticipated as emissions regulations become more stringent.
In operation, the oxygen sensor has a ceramic cylinder tip that measures the proportion of oxygen in the exhaust gas flowing out of the engine. Oxygen sensor measurements are most accurate when the sensor is heated to approximately 315-800° C. (600-1,472° F.), depending upon the type of oxygen sensor that is utilized. Accordingly, most sensors include heating elements to allow the sensor to reach an ideal temperature more quickly when the exhaust is cold. The temperature of the ceramic portion of the sensor varies with respect to the exhaust gas temperature in order to maintain accuracy of the sensor signal.
After measuring the proportion of oxygen in the exhaust gas, the sensor then generates a voltage signal representing the difference between the exhaust gas and the external air (i.e. air-fuel ratio). Depending on the style of sensor, the sensor may, instead, create a change in resistance signal to convey the same information. The signal is transmitted through signal wires to a powertrain control module (PCM) where it is compared with the stoichiometric air-fuel ratio (e.g. 14.7:1 by mass for gasoline) to determine if the air-fuel ratio is rich (e.g. unburned fuel vapor) or lean (e.g. excess oxygen). The PCM can then vary the fuel injector output to affect the desired air-fuel ratio and ultimately to optimize engine performance and control vehicle emissions.
Oxygen sensors are typically powered through the various attached wires. For example, signal wires and heater wires may provide power to the sensor and the heating elements, respectively. As emissions regulations become more stringent and more sensors are used, additional wiring may be necessary. The additional wiring provides added complexity, increased assembly costs, and increased natural resource consumption (e.g. copper and plastics). Additionally, sensor failure may occur at the various sensor wires (e.g. power wires, heater wires) due to improper wiring, connector corrosion, or wire failure. When an oxygen sensor fails, the PCM can no longer sense the air-fuel ratio, which directly influences vehicle performance, such as by the consumption of excess fuel.
In addition to failure because of the various sensor wires, location of the oxygen sensors in the exhaust system can also lead to premature failure of the sensor. The exhaust pipe has natural vibration that comes primarily from engine rotation and combustion, but vibration may also be transmitted from the road surface through the vehicle body. Vibration may cause serious damage to the sensor and reduce its lifetime.